The difficult subject of black family structure is back in the news. When Sen. Daniel Patrick Moynihan raised it nearly a generation ago he was flayed as a racist. The debate is past that now, yet the subject and its policy implications remain a source of great unease.

Over 40 percent of black families are now headed by women (as compared with perhaps 25 percent when Moynihan wrote). These families contain a third of the black population and half of all black children. They are, almost by definition, weak economic units. Their median income in 1984 was $8,648, and over 50 percent lived below the poverty line. For intact black families, by contrast, those in which both husband and wife were present, median income in 1984 was $23,418, and the poverty rate was about 14 percent. This second set of figures does not describe a perfect society. The median income of two-parent black families was lower by a fifth, their poverty rate twice as high as the comparable figures for whites. But the problems of these two-parent black families are manageable. The trend toward female-headed families seems much less so. The trend exists for whites as well, but has not reached the same critical mass.

Some theorists and politicians have fastened on these patterns in recent years to declare that there is little more an intervening government can or should do for blacks in this country. The shorthand is that the war is mostly over. They say that one segment of black society no longer needs the government's help and the other is largely beyond its reach. There is a shifting of blame in this. The bulk of the poverty in female-headed families is said to be the result not of discrimination by whites but of attitudes among the affected blacks. Those attitudes are said in turn to be problem that black leaders may be able to deal with, by admonition, but government cannot.

The debate was neatly framed last week by the National Urban League in its annual report on The State of Black America. That report takes the unusual step, for an advocacy document, of printing the other side. It includes an essay by Glenn Loury, professor in the Kennedy School of Government at Harvard University, on "the limitations of civil rights strategies" in any longer promoting the interests of minorities. Mr. Loury does not say there is no more discrimination in society or that there is no further role for government. His point is one of emphasis: not all black problems are racial in the traditional sense today, and not all are the kind that can be solved in legislatures and the courts.

The league does not so much dispute this as lean the other way. It replies in part that:

1.Median black family income in 1984 was 56 percent of white. That figure did indeed mask differences among blacks. But it remained true that, as a group, black families "had about 56 cents to spend for every one dollar white families had . . . which was two cents less than in 1980, and almost six cents less than . . . in 1970." It is not an equal society.

2.Intact black families, particularly younger ones, have gained appreciably on their white counterparts in recent years in median income. But their median incomes are still 10 to 20 percent less -- and then only because among the blacks there are more working wives. Where only one adult works, the median income of black two- parent families is 62 percent of white. The league would aggressively enforce affirmative action requirements.

3.Female-headed families are heavily dependent on Aid to Families with Dependent Children. AFDC benefits have lost ground to inflation and the poverty standard in recent years; their purchasing power has fallen by a third. The government should raise these payments.

But what the league wants most from government is jobs. It is for lack of jobs, it argues, that black men "don't get married . . . avoid responsibility . . . do not participate in the raising of families." The unemployment rate for black male teen-agers last year was over 40 percent, for young black male adults, almost 25 percent. "Unless we deal directly with black male unemployment," the league says, "we can only treat the symptoms of family disintegration."

Federal jobs programs are discredited these days, and have been mostly dismantled. The league would resurrect them. That is a costly and difficult approach to sell, or even to have much faith in. Can you build a sense of family on a wide scale with public programs of this kind? That is where the debate has come.